【導(dǎo)讀】本文我將論述一下嵌入式Linux目前的發(fā)展趨勢（狀況）。么，嵌入式Linux系統(tǒng)與桌面系統(tǒng)有什么不同的特點。然后，我將詳細(xì)地論述六。統(tǒng)管理社區(qū)，以及主流的非技術(shù)性新聞媒體上被廣泛宣傳和激烈的討論。植到許多不同的微處理器上并運行在許多并不含有硬盤的平臺上。正是這些類型的系統(tǒng)，被統(tǒng)稱為“嵌入式Linux”。在下一節(jié)我會關(guān)注嵌入式Linux系統(tǒng)和它的堂兄弟桌面Linux系統(tǒng)之間的區(qū)別。持，經(jīng)濟性，和技術(shù)支持這六個方面的特點。的嵌入式Linux內(nèi)核與WindowsCE內(nèi)核的大小和實時性特征。意見的作用和未來的嵌入式Linux。是不是如果系統(tǒng)不是從硬盤上啟動的就可以被稱為嵌入式系。本節(jié)將列出五個不同。注意，這些設(shè)備都不是專用于Linux的，但。從歷史上看，嵌入式系統(tǒng)的界定已經(jīng)成為一個巨大的，有爭議的灰色地帶。酒和大量的怪胎參加。嵌入式系統(tǒng)中至關(guān)重要的議題。另外，值得注意的是，嵌入式Linux可同時滿足這些要求。最后，嵌入式系統(tǒng)通常是針對一系列專門任務(wù)而設(shè)計的。

　　

【正文】 th real time features. They have a few features, such as periodic timers, that are not present in RTLinux but do not have the wide popularity of RTLinux. If you believe the rumors, these two products will merge in some future version. There are some problems with the features present in both RTLinux and RTAI. First of all it is clear that the features were bolted on as an afterthought instead of being an intrinsic part of the design. Although RTLinux does an admirable job of acplishing it’s goals it tends to be useful in certain classes of applications such as data acquisition rather then being more generally applicable. Another issue is that RTLinux does nothing to address the problem of priority inversion, which can be the cause of serious bugs that are hard to reproduce and track down. Figure 1: Block Level design of RTLinux Graphical User Interfaces As the desktop puter has e to rely on GUIs rather than text based interfaces, many embedded systems have also been adopting them. A GUI in an embedded system may e in many different flavors including small resolution LCDs, an optional VGA output port, or a fully integrated screen with either vertical or horizontal orientation. Although similar in concept to desktop GUIs, embedded systems have some requirements, such as the kernel footprint, that are uniquely their own. Linux has always suffered from a fragmented market in the area of GUIs. Although the XWindow the closest thing to a standard, there are many popular petitors including emulators for the Win32 API and the look and feel of Windows 95. Embedded systems are certainly free to use any of these systems that are targeted for the desktop, but there are several products that specifically target the unique needs of embedded systems. Lineo Systems is one provider of a version of embedded Linux with enhancements and mercial support. One of the options that they provide is a custom toolkit for building an embedded GUI. Microwindows and NanoGUI are two public, open source projects that were merged to provide a free library for emulating the Win32 API for use on Linux systems. There are certainly other options – these are just the tip of the iceberg. RealTime FIFOs Interrupt Control Hardware RealTime Kernel RealTime Tasks Linux Linux Processes There is another, separate route that many embedded devices have chosen to take when providing a GUI. Since work and Inter connectivity are so mon these days, many systems choose to include a web server and offer up their user interface via HTML. This allows the user to access the device remotely from any location with any platform that has a web browser. It also places fewer requirements on the size and shape of the device since it doesn’t have to include a display. Development Tool Support Embedded Linux developers get the best of both worlds when it es to development tools. Not only do they get to utilize the same GNU tool chain as their desktop brethren。 they can utilize the same hardware debugging tools they have always used. You don’t need to change your oscilloscope or logic analyzer just because you switch over to embedded Linux. The GNU collection of pilers, debuggers, assemblers and linkers represent a wide array of microprocessor support and one of the best proof of concepts that the open source munity has. Not only are they timetested and freely available, but the availability of source code means that if you want to port to a new processor you have the freedom to implement the piler support if it is not already available. Very few other embedded operating systems can match this claim, and even fewer do so with little to no up front cash requirements other than development time. There are a few snags. The GNU debuggers are mostly text based, with varying support for frameworks running on top of them for some platforms. Also, many people have found the GNU kernel debugger to be buggy and hard to use, which is especially frustrating for embedded system development where device drivers are very mon. Another difference for users of uCLinux is a special executable file format. Since there is no virtual memory, the executable cannot have relocations and all branches are done with position independent code (PIC). This requires a special linker and modifications to the debugging tools if the processor you are using is not already supported. Economic Considerations One of the biggest attractions of Linux in general is that it is free. Although you can buy versions from many panies that have more userfriendly installs or additional features, the core Linux code is free for downloading and is subject to the generous GNU redistribution license. This is true for both desktop and embedded Linux, but the embedded space does have some additional issues to consider. It is possible to incur royalty fees for distributing embedded Linux with your device, depending on your Linux supplier. Lineo’s Embedix has royalties that vary with the OS features and additional packages included such as their GUI toolkit and web browser. Also, device drivers for special hardware that are not included in the regular Linux distribution can be purchased from many different panies and have associated royalties. Although you could certainly write the drivers yourself, available resources and time to market can always influence your “build or buy” decision to go with the faster option. Considering these factors, your embedded Linux product may not be royalty free after all. Another concern that has sparked a lot of discussion in the Linux munity recently, is the fact that RTLinux is based on a patent. Although the RTLinux creators have stated that no